This application claims the priority benefit under 35 U.S.C. § 119 of Japanese Patent Application No. 2006-006350 filed on Jan. 13, 2006, which is hereby incorporated in its entirety by reference.
1. Field
The presently disclosed subject matter relates to a reflection type optical sensor which optically detects the surface roughness of an object by detecting the reflection of a light beam irradiated onto the surface of the object, and to a method for detecting the surface roughness of a surface to be measured, using the sensor. More particularly, the presently disclosed subject matter relates to a reflection type optical sensor that can function as a media sensor configured to identify the type of paper (such as ordinary paper, glossy paper, recycled paper, coated paper, and an OHP transparency film) for use in a color copier, a color printer, or the like. The disclosed subject matter can also function as a gloss sensor configured to measure the gloss of a painted surface or the like. In addition, the disclosed subject matter can function as a material identification sensor configured to identify types of materials of various components used in an FA field. In addition to these, the presently disclosed subject matter relates to a method for detecting the surface roughness of a surface to be measured.
2. Description of the Related Art
FIG. 1 is a schematic diagram of a conventional reflection type optical sensor 55 configured to include a light projection device 50, a light receiving device 51, a polarizing plate 52, a polarizing beam splitter 53, and a correction light receiving device 54. The light projection device 50 is provided with, as a light source, a light emitting device such as a light emitting diode (LED) or a laser diode, which emits a light beam of a single wavelength. The light receiving device 51 is provided with, as a photoreceptor, a light receiving element such as a photodiode or a phototransistor. The light projection device 50 and the light receiving device 51 are arranged such that the incident angle θ of the optical axis of the light projection device 50 is the same as the reflection angle θ of the optical axis of the light receiving device 51. Here, the incident angle and the reflection angle are determined with respect to the normal to the surface of an object. The light projection device 50 is provided with the polarizing plate 52 disposed on the optical axis of the light projection device 50 in the light irradiating direction. The light receiving device 51 is provided with the polarizing beam splitter 53 disposed on the optical axis of the light receiving device 51 on the light incident side. Furthermore, the correction light receiving device 54 is disposed at a position at which it can receive the light beam that is separated and reflected by the polarizing beam splitter 53.
In the reflection type optical sensor 55 having the above described configuration, the light beam emitted from the light projection device 50 which has a single wavelength is polarized when the light beam passes through the polarizing plate 52. In this case, the polarized light beam has a plane of vibration in a specific direction. This polarized light beam is irradiated onto an object surface 56. Then, the polarized light beam reflected from the object surface 56 is separated by the polarizing beam splitter 53, and the separated light beams are detected by the light receiving device 51 and the correction light receiving device 54, respectively, to produce output signals.
The reflection type optical sensor 55 is configured such that, among the polarized light beams reflected from the surface 56 of the object to be measured, the reflected polarized light beam that has the same plane of vibration as that of the polarized light beam which passed through the polarizing plate 52 is detected by the light receiving device 51 through the polarizing beam splitter 53. Furthermore, the reflected polarized light beam that has a different plane of vibration from that of the polarized light beam which passed through the polarizing plate 52 is detected by the correction light receiving device 54 through the polarizing beam splitter 53.
Therefore, by computing the ratio of the output of the light receiving device 51 based on the amount of the received polarized light beam to the output of the correction light receiving device 54 based on the amount of the received polarized light beam, the surface roughness of the object to be measured can be detected (see, for example, Japanese Patent Laid-Open Publication No. Hei 10-281991).
The reflection type optical sensor as described above is capable of identifying different types of printing media such as ordinary paper, glossy paper, recycled paper, coated paper, and an OHP transparency film. Furthermore, since the detection resolution is very high, the different types of glossy paper which is one of the printing media can be more particularly identified based on the gloss thereof.
However, the above described reflection type optical sensor has polarizing optical elements (the polarizing plate and the polarizing beam splitter) as components. Therefore, a problem exists in that the manufacturing cost associated with multiple elements is high.